Rotary disk mowers are well known and widely used and typically include a transverse cutter bar defined by a support beam and a gear casing carried on the beam with the gears acting to drive the rotary disks about vertical axes along the cutter bar. Underneath the cutter bar is provide a series of rock guards which underlie the cutter bar and act as replaceable wear guards to protect the cutter bar. A number of examples of such rock guards are shown in the prior art.
U.S. Pat. No. 4,709,540 (Collart) issued Dec. 1, 1987 and assigned to Zweegers discloses a mowing device has a number of adjacent cutter disks rotatable around upwardly extending axes of rotation of a cutter bar. The cutting disks are supported by an elongated hollow gear casing located under the cutting disks with gears for driving at least some of the cutting elements located in the casing. A reinforcing beam, extending along the rear side of the casing, is fixed to said casing and carries the rear ends of tensioned resilient straps extending transverse to the beam and under the casing and joined to the casing near their front ends at the side of the casing away from the reinforcing beam. The straps support a protective plate underneath the cutter bar and extending along its full length
U.S. Pat. No. 7,661,253 (Pruitt) issued Feb. 16, 2010 and assigned to AGCO discloses a modular rotary cutter bed formed by a series of identical cutter modules mounted end-to-end along the length of a common support beam. Guards for the cutters of the modules are arranged underneath the cutter bar side by side along the cutter bar. Each guard overlaps and bridges the seam between an adjacent pair of modules so as to increase the structural rigidity of the cutter bed. Each guard is attached at its front end to the noses of a pair of adjacent modules and at its rear end to the support beam to increase structural integrity in all directions. A second embodiment does not utilize a common support beam for the modules but instead relies upon the interconnections between adjacent modules and the bridging overlap of the guards to make the cutter bed rigid.
In European 1 369 019 (Epp) assigned to Claas and published Oct. 12, 2003 is disclosed an arrangement in which a series of rock guard elements are arranged side by side across the cutter bar and fastened to the structure at the rear so as to extend forwardly therefrom to a forward edge underneath the cutter disk.